sch_gred Queuing Discipline
Generalized Random Early Detection Queues.
It was introduced to provide drop probability which was not provided by RED.
It maintains a set of virtual queues(VQ) within a physical queue.
It uses the last four bits in skb->tc_index to select the virtual queue.
It is a more general form of RED for the following reason
- DWRED (CISCO protocol) does the selection of the VQ based on the precedence bits. Also, there is a limit on the number of VQs.
But sch_gred offers the flexibility to do the selection based on the metering or on the classification. It is for this reason that it is named Generalized RED.